My electric panel is 100amps. My house does not have gas, so I have electric oven and dryer. I also have central A/C. My house is a ranch, around 1600 square feet. All of my appliances are recent, so Energy Star. I only have LED bulbs, a few CFLs. Electrician came over and is going to put in a 50amp dual pole breaker so I can put in a NEMA 14-50.
Am I pushing my luck with the load or should I go with a NEMA 14-30. Now mind you, I am most likely going for the Model 3 LR, not the SR+, if that makes any difference. I would charge overnight when neither the dryer nor the oven would be running, but surely the A/C would come on intermittently overnight.
Any advice?
I am super conflicted on this one. I could argue this multiple ways. My recommendation would vary based on some additional information not yet included in this thread.
Can you post pictures of the following: Where the power comes into the house where the meter base is. Want to see conductor gauges for the aerial drop and run down the mast if overhead, or at least the conduit coming out of the ground if underground. Want to see what kind of meter and meter base you have. Then I want to see your electrical panel (or panels) in such a way as to see all the amperages on the breakers, and the circuit inventory, and any stickers providing the gory details about the panel specifications. This helps us determine if the panel is a known dangerous on among other things and what vintage it is. In an optimal world we would have pictures with the panel cover removed, but don't do this unless you have experience and comfort with that procedure.
What year was the house built/renovated (want to know age of electrical service/panel)?
As many have mentioned, what needs to be done is a true NEC load calculation to see where you fall right now with existing loads. If you put in a NEMA 14-50 receptacle and intend to use it with a UMC Gen 2 then you need to calculate it as a 32a continuous load. (it does not matter if it is on a 40a or a 50a circuit, it is still calculated as 32a continuous)
I could argue here that you might squeak by on the load calc side since your major heating loads (furnace and water heating) sound like they are heating oil? So not electric...
There are a lot of folks that successfully charge EV's on 100a services. (but the question is - how fast?)
Part of me says that if an electrician is willing to do a 50a circuit with 6 awg wire and have it permitted and signed off on, then I might just be willing to go for that. You still would have the option of manually setting the current lower in the car to add a margin of safety. I might be tempted to do this if the electrical service was modern good quality equipment and so manually reducing the amps was just adding further margin of safety. I would say that a lot of NEC load calculations sometimes result in some pretty under-utilized electric services (though this is partially compensated for by exceptions that let you reduce service conductor sizes after the calculation - and it is probably less likely to oversize on small services like 100a).
You could also run 6 AWG wire, but just do a 14-30 receptacle and 30a breaker for now (I think others have suggested this). It would require the proper $35 Tesla UMC adapter. This gives you easy upgradability.
I may also recommend getting a Sense Home Energy Monitor and installing it in order to get a better idea of what is actually going on. Having this in my house has made me realize how little of my 200a electrical service I actually use. I could probably just about get by on a 100a electrical service even with my M3 LR and Wall Connector on a 60a circuit charging at 48a. (but literally everything in my house that can be gas is gas)
How long to you plan to own / live in the house? This is another factor that really plays into this. Depending on my future plans for a house and how old the existing electrical service would weigh heavily on my decisions to upgrade the main service or not. I personally like overkilling things like this since I just don't want to worry about it, but I also am cheap. ;-) It is a fixed cost though with a very long capital lifespan to amortize it over.
I am going to throw out another possible option: You could do a Wall Connector on say 6 awg copper in conduit on a 60a circuit. This would nearly surely be too much load for your current electrical service, but you could have the electrician crank down the maximum Wall Connector rotary dial setting to whatever level the load calculations allowed you to use (say crank it to 32a continuous, or even 24a continuous). While the capital cost of this install is higher, it would provide a lot of flexibility. You could tune it to just the right amperage that your service supports and you could change it over time if other factors changed (like switching to a gas dryer, upgrading the service to 200a, etc...)
A note on the dryer buddy: I don't think it is UL approved or anything, so just food for thought. I like the concept, though I would have to go look at how dryers are factored into the load calcs compared to EV's. Dryers may have some kind of a load factor applied to them that does not apply to EV's, so I am not sure that just having a dryer buddy "solves" the load calculation issue (though it most certainly helps). My general thesis though is that I prefer spending money on "copper" (wire) than on electronics that have a shorter lifespan. ;-)
While I am typically really conservative, I would be somewhat tempted to do the 14-50 or Wall Connector on a 60a circuit (but cranked down on the hardware dial setting) as in special conditions it might allow me to violate some rules to charge faster. ;-) For instance, I would have zero issues charging overnight at 32a if you are not running the AC... Especially if you had a Sense Energy Monitor to see what was going on in real time, it may give me a lot of comfort. Also, while I never advise relying on this exclusively, you do have a main 100a main breaker right? If a modern unit from a reputable brand the odds are it would protect you. Also, depending on your main panel, the failure mode might be in an external metal box in metal conduit, so failures are less likely to result in a structure fire.
Regardless of what you do, please report back! Cheers!
